1. Field of the Invention
The present invention relates to an image recording apparatus such as a copying machine, a printer device and a plotter device, and more particularly to a device for providing imaging material particles such as toner particles on a support member. The term "imaging material particles" as used herein includes toner particles, developer material particles, etc. for forming a visible image.
2. Description of the Related Art
Various kinds of image recording apparatuses are provided with devices for providing imaging material particles on support members. There has been conventionally known the imaging material providing device of the type in which charged imaging material particles are carried on a carry member, a support member is mounted on a mount member such that the support member may confront the carry member with a gap therebetween, and an electric field is produced in the gap so that the charged imaging material particles are electrostatically attracted toward the support member with the electric field to thereby be attached onto the support member.
As one example of the imaging material providing device, there has been proposed an image recording device provided with a plurality of control electrodes each having an aperture. The control electrodes are placed between a toner carry member and a support member mount member. The carry member carries thereon charged imaging material particles such as toner particles. Image signals are applied to the control electrodes to selectively charge the electrodes to a second polarity opposite to the polarity of the toner particles to thereby produce electric fields between the carry member and the control electrodes. The toner particles carried on the carry member are electrostatically attracted to the control electrodes with the electric fields, and pass through the apertures on the control electrodes to reach the support member on the mount member. The toner particles attached to the support member form a visible toner image corresponding to the image signals.
In the above-described image recording device, it is necessary to convey the toner particles to portions near to the apertures of the control electrodes where electric fields are produced. There have been conventionally proposed various types of manners how the toner particles are conveyed to the portions near to the apertures.
For example, a Japanese Patent Unexamined Application Publication No. 62-248662 proposes that the toner carry member comprises a roller-shaped member on the surface of which the charged toner particles are carried, and the roller-shaped carry member is rotated to convey the toner particles to the portions near to the apertures. In this case, however, adhesion force of the toner particles to the surface of the roller is relatively large, and therefore high voltage is required to be applied to the control electrodes to attract the toner particles. As a result, it is necessary to mount a high voltage power supply in the image recording device.
A Japanese Unexamined Patent Application Publication No. 58-44457 proposes another type of manner of conveying the toner particles to the portions near to the apertures that an alternate electric field is produced between the toner carry member and the control electrodes so that the toner particles may be changed into mist form to be conveyed to the portions near to the apertures. In this case, however, the applied alternate voltage disturbs the electric fields generated by the image signals, as a result of which it becomes impossible to obtain a clear image. Furthermore, such a device is made expensive, since it is necessary to mount an AC high voltage power supply in the device.
A Japanese Unexamined Patent Application Publication No. 58-114974 proposes that a flow of air conveys the toner particles to the portions near to the apertures. In this case, however, it becomes necessary to provide the image recording device with a unit for generating the air flow such as an air compressor unit, as a result of which the device as a whole becomes complicated and expensive.
Another example of the device for electrostatically providing the imaging material particles to the support member is utilized as a unit for producing a developer sheet from a support member which is a plain paper selected arbitrarily by an user. The developer sheet producing unit is mounted in an image forming apparatus such as a color copying machine. In this type of image forming apparatus, a microcapsule sheet is exposed to light to form a latent image thereon, and is superposed on the developer sheet which has been previously produced in the developer sheet forming unit. The superposed sheets are subjected to pressure development action to form a visible toner image on the developer sheet which is then thermally fixed in a heat fixing unit.
In the imaging material providing device applied as the developer sheet producing unit, the support member is mounted on a mount member, charged imaging material particles (such as charged developer material particles) are carried on a carry member, and an electric field is produced in a gap between the support member mount member and the charged developer material carry member. The charged developer material particles carried on the carry member are electrostatically attracted to the support member with the electric field. The support member is conveyed by the mount member, and the entire surface of the support member is coated with the developer material particles to produce a developer sheet.
In the imaging material providing device as constructed above, the carry member conveys the charged imaging material particles to the region where the electric field occurs. As the imaging material carry member, one of the co-inventors of the present invention proposes, in the copending U.S. patent application Ser. No. 07/498,761 filed on Mar. 26, 1990 (not prior art), such a carry member as comprising a brush-shaped roller with its peripheral surface having a number of ciliary members implanted thereon. According to the carry member of the type, the developer material particles can be filled in gaps between neighboring ciliary members, so that a lot of developer material particles can be conveyed toward the region where the electric field occurs.
Such a imaging material providing device using a brush roller, however, has a problem that the developer material particles jam in gaps between neighboring ciliary members of the brush roller in the case where the device is operated for a long time. As a result, the amount of the developer material particles conveyed by the electric field to be attached onto the support member is decreased, so that it is impossible to produce a developer sheet coated with sufficient amount of developer material particles.